The adverse effect of thinner on the composite quality and the solution

The main role of the diluent is to reduce the viscosity of the adhesive for coating, application, and also to extend the life of the adhesive. Diluents are divided into two types of non-reactive diluents and reactive diluents.

(1) Inactive diluents (generally referred to as solvents) do not participate in the curing reaction of the adhesive.

(2) Reactive diluents, which can reduce the viscosity of the adhesive, participate in the curing reaction of the adhesive, and enter the mesh or body structure of the resin, thus overcoming the problem of incomplete adhesive evaporation. The disadvantage of decreased composite strength.

When the binder is diluted with a solvent, its volatilization rate should be taken into account, and the volatilization rate must not be too fast or too slow. If the volatilization is too slow, the solvent remains in the glue gap after curing, thereby affecting the composite strength of the adhesive.

If it is to be completely volatilized, the drying time is too long and the production efficiency is low; if the volatilization is too fast, the adhesive is difficult to coat, and when the humidity in the air is too high, the volatilization of the solvent takes away. A large amount of heat on the adhesive surface of the glue tank and the substrate causes the adhesive surface temperature of the substrate to be lower than the ambient temperature. In this way, the water vapor in the air will condense on the surface of the adhesive, so that the adhesive layer Whitening results in reduced composite strength after bonding. Therefore, when the relative humidity in the air is greater than 85%, construction should not be carried out or appropriate dehumidification protection measures should be taken.

The amount of diluent has an effect on the properties of the adhesive. The amount is too much, because the medium and low molecular weight components in the adhesive system are many, hindering the crosslinking reaction when the adhesive is cured, and affecting the performance of the adhesive, especially during use, since one side of the resin is Curing, the solvent must be volatilized from the adhesive system, so the shrinkage of the adhesive is increased, and the composite strength, heat resistance and media resistance of the adhesive are reduced.